1. Field of the Invention
The present invention relates to a mold for production of a thermoplastic resin molded article having a hollow part, and a process for production of a thermoplastic resin molded article having a hollow part using the same mold. Hereinafter, a hollow thermoplastic resin molded article and a thermoplastic resin are referred to as "hollow molded article" and "resin", respectively.
2. Description of Related Art
Hollow molded articles have been produced, for example, by feeding molten resin into a cavity of a mold, provided with a movable or fixed gas introducing pin, as shown in FIG. 16, and directly introducing compressed air or high-pressure gas into the molten resin through a tip of the gas introducing pin which protrudes into the cavity (see, for example, JP-A 3-164222 and JP-A 5-16177).
However, the mold used in this method is costly due to the presence of the gas introducing pin and the design of the mold is restricted due to the larger space occupied by the gas introducing member in the mold. In addition, since a gas-ejecting hole of the gas introducing pin is easily choked with resin, maintenance of the gas introducing pin is costly and time consuming. In addition, a trace formed by pulling out the gas introducing pin after molding remains on the surface of the hollow molded articles produced by this method. Further, choking of the gas-ejecting hole with resin prevents gas introduction, which decreases the amount of introduced gas and leads to formation of an insufficient hollow part.
The object of the present invention is to provide a mold which can successfully form a hollow part in the interior of a thermoplastic resin molded article and yield a hollow molded article having a good appearance and a process for production of a hollow molded article using the same mold.
This object as well as other objects and advantages of the present invention will become apparent to those skilled in the art from the following description with reference to the accompanying drawings.